''Alaskoceras'' is a genus of lower

Ordovician The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start ...

coiled

nautiloid Nautiloids are a group of marine cephalopods ( Mollusca) which originated in the Late Cambrian and are represented today by the living ''Nautilus'' and ''Allonautilus''. Fossil nautiloids are diverse and speciose, with over 2,500 recorded species ...

cephalopods; the shell moderately expanded, ribbed, with a divergent living chamber; whorl section more broadly rounded ventrally than dorsally;

siphuncle The siphuncle is a strand of tissue passing longitudinally through the shell of a cephalopod mollusk. Only cephalopods with chambered shells have siphuncles, such as the extinct ammonites and belemnites, and the living nautiluses, cuttlefish, and ...

marginal at maturity, septal necks short, almost achoanitic; connecting rings thick, layered. ''Alaskcoceras'' belongs to the

Tarphycerida The Tarphycerida were the first of the coiled cephalopods, found in marine sediments from the Lower Ordovician (middle and upper Canad) to the Middle Devonian. Some, such as '' Aphetoceras'' and '' Estonioceras'', are loosely coiled and gyroconi ...

, and to the family Estonioceratidae. It was found in Alaska.

References

* W.M Furnish & Brian F. Glenister, 1964. Nautiloidea-Tarphycerida. Treatise on Invertebrate Paleontology, Part K. Geological Society of America and University of Kansas Press. Ordovician cephalopods of North America Prehistoric nautiloid genera {{paleo-nautiloidea-stub